A Microprocessor-Based Time Optimal Control of A Variable-Reluctance Step Motor

A time optimal control of a single-stack variable-reluctance step motor by a microprocessor is described. To execute a random move length in minimum or quasi-minimum time in open-loop control, the microprocessor controls the motor velocity by referring and, if necessary, connecting the precalculated and stored acceleration and deceleration tables. This control scheme causes, however, a poor settling when the move length becomes much shorter than the one required for full acceleration and deceleration. To overcome this drawback, a new technique is presented which uses auxiliary tables only for move lengths corresponding to Fibonacci numbers. Acceleration, deceleration, and auxiliary tables are obtained by computer simulation, then stored in the microprocessor's memory. It is shown how effectively such smaller move lengths are executed by using the auxiliary tables. No external circuitry is necessary except a power drive circuit in this system as the microprocessor works as a four-phase translator, a step counter, and a clock generator.